No abstract

Polypeptide nanoparticles were obtained by the miniemulsion polymerization of S-(o-nitrobenzyl)-L-cysteine (NBC) N-carboxyanhydride (NCA). Through process optimization, reaction conditions were identified that allowed the polymerization of the water sensitive NCA to yield nanoparticles of about 220 nm size. Subsequent UV-irradiation of the nanoparticle emulsions caused the in situ removal of the nitrobenzyl group and particle cross-linking through disulfide bond formation accompanied by the shrinkage of the particles.

The synthesis of hybrid bioconjugates via the ring-opening polymerization (ROP) of N-carboxyanhydrides (NCAs) using a synthetic macroinitiator is described. Poly(n-butyl acrylate), polystyrene, and poly(N-isopropyl acrylamide) are synthesized (polydisperity index, Đ < 1.1) using reversible addition-fragmentation chain transfer (RAFT) as the synthetic tool. A phthalimidomethyl trithiocarbonate RAFT chain transfer agent is used to prepare well-defined, end-functional polymers, which after deprotection result in amine terminal macroinitiators. The subsequent initiating systems could successfully be chain extended with ε-benzyloxycarbonyl-l-lysine or γ-benzyl-l-glutamate as the NCAs to produce a library of polymer-polypeptide conjugates. In doing so, a novel procedure for directly synthesizing bioconjugates via a non-modular route without the need for excessive purification and isolation steps is described.

A new approach for the fabrication of luminescent ratiometric sensing nanosensors is described using core-shell nanoparticles in which the probe and reference are spatially separated into the shell and core of the nanostructure respectively. The isolation of the reference in the core of the particle ensures a stable emission reference signal unaffected by the external environment. The core shell structure was prepared by engineering structurally well-defined Ru-conjugated block copolymers which acted as emulsifiers in the miniemulsion polymerisation of BODIPY loaded styrene nanoparticles. The resulting particles are highly stable and show excellent size monodispersity. The nanosensors exhibit dual emission under a single excitation wavelength with a reversible and quantitative ratiometric response to the O content in aqueous media. In the presence of a low concentration of CTAB, the particles cross the cell membrane and the particles show negligible cytotoxicity. Such an approach to sensor nanoparticles should be of value across a range of applications where a stable ratiometric signal in diverse environments is required.